Circuit board assembly for a liquid submersion cooled electronic device

ABSTRACT

A circuit board assembly, for example, a computer motherboard, for use in a liquid submersion cooled electronic device, for example, a computer, is configured to facilitate movement of the cooling liquid when the circuit board is submerged in the cooling liquid, thereby improving the heat transfer from heat-generating components on the circuit board. For a computer, a plurality of heat-generating components are mounted on the motherboard, including a plurality of processors, a plurality of memory cards, a plurality of graphics cards, and a plurality of power supplies. A pump for the cooling liquid can also be mounted on the motherboard.

This application claims the benefit of U.S. Provisional Application60/800,715 filed May 16, 2006, which is incorporated by reference hereinin its entirety.

TECHNICAL FIELD

This disclosure relates to a liquid submersion cooling system, and inparticular, to a circuit board assembly used in a liquid submersioncooled electronic device, for example, a computer.

BACKGROUND

A significant problem facing the computer industry is heat. The higherthe temperature a component operates at, the more likely it is to fail.Also, high temperatures, while not causing catastrophic failures, cancreate data processing errors. Operation at high temperatures can causepower fluctuations that lead to these errors within a central processingunit (CPU) or on the motherboard anywhere that data management ishandled. Despite efforts at reducing waste heat while increasingprocessing power, each new CPU and graphics processing unit (GPU)released on the market runs hotter than the last. Power supply andmotherboard components required to provide power and handle signalprocessing also are producing more and more heat with every newgeneration.

The use of liquids in cooling systems to cool computer systems is known.One known method of cooling computer components employs a closed-loop,2-phase system 10 as illustrated in FIG. 1. The 2-phase system 10 isemployed to passively cool the north 12 and south 14 bridge chips. Thevapor travels through a tube 16 to a cooling chamber 18, the vapor turnsback into liquid, and the liquid is returned by tube 20 to the chips 12,14 for further cooling. In another known liquid cooling system, internalpumps move liquid past a hot plate on a CPU and then the heated liquidis pumped into a finned lower that passively cools the liquid andreturns it to the plate.

In the case of large-scale, fixed-installation supercomputers, it isknown to submerge the active processing components of the supercomputerin inert, dielectric fluid. The fluid is typically allowed to flowthrough the active components and then it is pumped to external heatexchangers where the fluid is cooled before being returned to the mainchamber.

Despite prior attempts to cool computer components, further improvementsto cooling systems are necessary.

SUMMARY

A portable, self-contained liquid submersion cooling system is describedthat is suitable for cooling a number of electronic devices, includingcooling heat-generating components in computer systems and other systemsthat use electronic, heat-generating components. Examples of electronicdevices to which the concepts described herein can be applied include,but are not limited to, desktop computers and other forms of personalcomputers including laptop computers, console gaming devices, hand-helddevices such as tablet computers and personal digital assistants (PDAs);servers including blade servers; disk arrays/storage systems; storagearea networks; storage communication systems; work stations; routers;telecommunication infrastructure/switches; wired, optical and wirelesscommunication devices; cell processor devices; printers; power supplies;displays; optical devices; instrumentation systems, including hand-heldsystems; military electronics; etc.

The electronic device can include a housing having an interior space. Adielectric cooling liquid is contained in the interior space, and acircuit board assembly is disposed within the space and submerged in thedielectric cooling liquid. The circuit board assembly includes a circuitboard, and a plurality of components mounted on the circuit board. Thecomponents mounted on the circuit board can include one or more of aplurality of processors, a plurality of memory cards, a plurality ofgraphics card, and a plurality of power supplies. In certainembodiments, a liquid pump can also be mounted on the circuit board.Other components could be mounted on the circuit board as well, forexample, light-emitting diodes and one or more hard drives.

When the electronic device is a computer, for example, a personalcomputer, the circuit board is a computer motherboard. The components onthe motherboard are arranged on the motherboard relative to each otherso as to facilitate the movement of the liquid within the housing,thereby increasing heat transfer. In particular, the components arearranged to define a first plurality of liquid flow channels parallel toan axis of the motherboard and a second plurality of liquid flowchannels perpendicular to the axis.

In certain embodiments, one or more heat sinks can be connected to theheat-generating components on the circuit board. The heat sinks helpmitigate heat and are designed to facilitate the flow of the liquid inthe housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cooling system employing a 2-phase system 10 to passivelycool the north and south bridge chips.

FIG. 2 is a view of an embodiment of a liquid submersion cooling systemon a personal computer.

FIGS. 3A and 3B are perspective and end views, respectively, showingcomponents of the liquid submersion cooling system of FIG. 2.

FIG. 4 is a perspective view of the computer case.

FIGS. 5A, 5B, and 5C are perspective, top and side views, respectively,of the lid of the computer case showing the pass-through connector.

FIG. 6 is a detailed illustration of the pass-through connector.

FIG. 7 is a perspective view of the motherboard or circuit board of thecomputer.

FIGS. 8A and 8B are perspective and side views, respectively, showingdaughter cards on the motherboard and showing engagement with the lid.

FIG. 9 illustrates a subassembly including the case, motherboard anddaughter cards in the case, and the lid.

FIG. 10 illustrates the subassembly of FIG. 9 with a pump within thecase.

FIGS. 11A and 11B are perspective and end views, respectively, of asubassembly that includes a hard drive within the case.

FIGS. 12A and 12B are perspective and end views, respectively, of asubassembly that includes multiple heat exchangers.

FIGS. 13A and 13B are perspective and end views, respectively, of asubassembly that includes a single heat exchanger.

FIG. 14 is an end view similar to FIG. 12B showing how convectioncooling works.

FIG. 15 is an illustration of a prototype computer that incorporates theliquid submersion cooling system, where the video boards and pump arevisible in the case and the radiators are visible, mounted on the sides.

FIG. 16 is an illustration of the prototype computer of FIG. 15 showingthe front and top of the case.

FIG. 17 is a perspective view of another embodiment of a liquidsubmersion cooling system on a personal computer.

FIG. 18 is a side view of the computer shown in FIG. 17.

FIG. 19 is an end view of the computer shown in FIG. 17.

FIG. 20 is a perspective view similar to FIG. 17 but with themotherboard assembly partially lifted from the interior space.

FIG. 21 is an end view of the motherboard assembly removed from thecomputer.

FIG. 22 is a perspective view of the motherboard assembly.

FIG. 23 is a side view of the motherboard assembly.

FIG. 24 illustrates the motherboard assembly in a raised position.

FIG. 25 is a perspective view of the computer case with the motherboardassembly and lid removed.

FIG. 26 is a side view of the heat exchanger.

FIG. 27 illustrates a pair of heat exchanger plates used to form theheat exchanger.

FIG. 28 is a perspective view of the heat exchanger and fan.

FIG. 29 illustrates a snorkel attachment for use with a hard drive.

FIGS. 30A, 30B, and 30C illustrate use of the snorkel attachment on ahard drive.

FIGS. 31A, 31B and 31C illustrate details of the AC current cut-offmechanism associated with the lid.

DETAILED DESCRIPTION

A liquid submersion cooling system is described that is suitable forcooling a number of electronic devices, including coolingheat-generating components in computer systems and other systems thatuse electronic, heat-generating components. In the case of computersystems, the liquid submersion cooling system permits creation of, forexample, desktop-sized computers with scalable architectures where it ispossible to produce 32 to 64, or more, processor core systems (8sockets×8 cores=64 processor). The processing power of thesedesktop-sized computer systems will rival or surpass supercomputingsystems that, until now, would require significant floor space.

Examples of electronic devices to which the concepts described hereincan be applied include, but are not limited to, desktop computers andother forms of personal computers including laptop computers; consolegaming devices, hand-held devices such as tablet computers, wearablecomputers and personal digital assistants (PDAs); servers includingblade servers; disk arrays/storage systems; storage area networks;storage communication systems; work stations; routers; telecommunicationinfrastructure/switches; wired, optical and wireless communicationdevices; cell processor devices; printers; power supplies; displays;optical devices; instrumentation systems including hand-held systems;military electronics; etc. The concepts will be described andillustrated herein as applied to a desktop-sized computer. However, itis to be realized that the concepts could be used on other electronicdevices as well.

FIGS. 2, 3A and 3B illustrate one embodiment of a desktop-sized computer20 employing a liquid submersion cooling system 22. All activecomponents are illustrated submerged in a tank of dielectric liquid.This system uses a dielectric cooling liquid in direct contact with theelectronically and thermally active components of a computer system.Dielectric liquids that can be used in this type of immersive coolingsystem include, but are not limited to:

-   -   Engineered fluids like 3M™ Novec™    -   Mineral oil    -   Silicone oil    -   Natural ester-based oils, including soybean-based oils    -   Synthetic ester-based oils        Many of these dielectric fluids also have the ability to        extinguish fires on computer components. By submerging computer        components in a dielectric, fire-retardant fluid, the chance of        a fire starting due to computer component failure is minimized.

Initial testing has involved the dielectric liquid 3M™ Novec™. However,other dielectric liquids, like mineral oil and ester-based oils, may beused. Other dielectric liquids that have a higher boiling temperaturealong with greater thermal transfer capability can be employed. Thesecooling liquids need not change state if they have a high enough thermaltransfer capability to handle the amount of heat being generated bycomponents contained in the system.

The lid 2 of the case 1 will attach to the connector side of thecomputer motherboard 30, shown in FIGS. 7, 8A and 8B, allowingmotherboard input/output (IO) connections, daughter card 4 IO and powerto be passed in and out of the system. Components such as daughter cards4, additional processors 6, power supply card 5, and memory cards 8 canbe added to the system by opening the tank lid 2 and lifting theattached electronics out of the case 1. In addition, a hard drive 11 canbe disposed in the case 1, with an air line 10 connected to the harddrive breather hole leading from the hard drive to the exterior of thecase 1.

At least one pump 13 will pump warm liquid from the top of the case 1and pass it through surrounding heat exchangers 3. The pump 13 may besubmersed in the liquid as shown in FIGS. 3B and 10, or external to thecase 1. Using two external pumps 13 with quick-release hose attachmentswould allow hot-swapping of a failed pump while the other pump maintainssystem circulation. Using one external pump 13 with quick-release hoseattachments would allow the change-out of a failed pump with only abrief system downtime.

The heat exchangers 3 can act as the outside surface and supportingstructure of the computer case 1. The majority of the case wall may actas a radiator surface. Unlike current Advanced Technology Extended (ATX)or Balanced Technology Extended (BTX) cases that push air through fansfrom the front of the case to the back, the disclosed system will takecold air from the base of the case and, aided by natural convection,pull more air up as intake air is heated and rises. The walls of theheat exchangers 3 may be tapered upward, like a cooling tower on aboiler. This tapering will help accelerate convection currents, makingit possible to cool the system without the use of air-moving devices,such as fans.

As shown in FIGS. 3A and 3B, the case 1 is large enough to contain allof the active computer components that require cooling. It may also benecessary to leave space for liquid return lines 48 with nozzles overcritical components that require cooling. Nozzles may be incorporated todirect the flow of the return liquid at specific, high-temperature areaslike the CPUs.

As shown in FIGS. 5A-C, 6 and 9, the lid 2 not only provides a liquid-and gas-tight seal for the case 1, but it also contains a pass-throughconnector 7 that allows external component IO, storage IO and power topass into and out of the case 1, to and from the computer motherboard 30and its components. The lid 2 will have a gasket that will seal the case1. The lid 2 may also contain a fill port 32 for filling the case 1 withcoolant.

As shown in FIGS. 7, 8A and 8B, the motherboard 30 is essentiallyfunctionally the same as in current ATX or BTX specification boards,with the exception being that it does not have the same IO and powerconnectors. Instead, the top edge of the board is lined with a series ofconductive pads 34 that are contacts for engaging the pass-throughconnector 7 that is part of the lid 2. Multiple motherboards or othercircuit boards may be employed to allow stacking of extra processors 6or other components for additional computing power or to allow formultiple computers within a single tank enclosure. This cooling systemwould allow for numerous computer systems to be cooled in a single tankor individual tanks which may be interconnected to create a server orworkstation rack system.

As shown in FIGS. 8A and 8B, the daughter cards 4 connect to themotherboard 30 as they do with current ATX or BTX specification boards.Daughter cards 4 can include video cards and other PCI or PCIE cardsthat require IO pass-through to the outside of the case 1. Thesedaughter cards 4 will require liquid- and gas-tight gaskets in order toallow external IO connections.

Unlike ATX or BTX designs, the power supply 5 may also be a daughtercard 4, with no power supply to motherboard wiring required. The powersupply may also be directly integrated into the motherboard. Externalalternating current (AC) connections would be made through apass-through connector into the liquid-filled tank with a liquid andgas-tight gasket.

As shown in FIG. 9, the pass-through connector 7 is integrated into thelid 2 in such a way that it creates a liquid- and gas-tight electricalconduit for IO and power connectivity. It attaches to the motherboard 30on the inside of the case 1 and leads to a connector break-out 36 on theoutside of the tank 1.

The pump 13 (or pumps) is either internally-mounted within the case 1,submersed in the liquid as shown in FIG. 10, or externally mounted. Thepump is used to circulate warm coolant from inside the tank 1 to outsideof the tank 1 within the heat exchangers 3. Liquid may also becirculated through external hard drive cooling plates as well. The pump13 can be wired such that it can be turned on to circulate liquid evenif the computer is off. Or the pump 13 can be wired to turn on only whenthe computer is on. After the computer is shut off, there is more thansufficient thermal capacity in the liquid within the case 1 to removeresidual heat from the submerged components. This would ensure thatthere is no post-shut down thermal damage. Also, if a flow sensor orpump monitor indicates that flow of coolant has stopped or has slowedbelow a minimum required rate, a controlled shutdown of the computercould be completed well before any damage is done to the submergedcomponents. This embodiment avoids the possibility of a fan failure,resulting in catastrophic failure of a computer that relies on aircooling.

As shown in FIG. 10, the pump 13 is illustrated in the lower left cornerof the case 1. Warm coolant is pumped from the top of the tank 1 tooutside of the tank 1 into the heat exchangers 3. The pump(s) 13 mayalternatively be attached to the lid 2 of the computer. This would allowfor direct intake of fluids from the warmest region of the tank 1 andmake maintenance and replacement of warn-out pumps much easier.

As shown in FIGS. 11A and 11B, the hard drives or other internal storagesystems 11 can also be submerged. In the case of current platter-based,mechanical storage systems that require breather holes, the air line 10could be fixed over the breather hole, allowing an open-air connectionto the outside of the tank 1. The rest of the drive 11 would be sealedas to be gas and liquid impermeable.

The processors 6 mount to the motherboard 30 via normal,vender-specified sockets. Testing has shown that no heat sinks or otherappliances need to be attached to the processors 6 in order to cool themsufficiently for normal, vendor-specified temperatures. However, iflower operating temperatures or a higher level of heat transfer isrequired for processor 6 over-clocking, heat sinks, which greatlyincrease the exposed surface area of heat conduction from theprocessor(s) 6, may be employed.

As shown in FIGS. 12A and 12B, the heat exchangers 3 or heat exchangersurfaces may serve as the external shell or case of the computer 20,When warm cooling liquid is pumped from within the case 1 to the heatexchangers 3, the liquid is cooled to ambient temperature. Cooling ofliquids utilizing a heat exchanger 3 can be accomplished by one ofseveral means:

-   -   A compressor, as is the case with typical refrigeration systems    -   Peltier effect cooling    -   Active air cooling of the radiator surface using a fan or other        air-moving mechanism    -   Passive cooling by exposing as large of a thermally conductive        heat exchange surface as possible to lower ambient temperatures

As shown in FIGS. 12A, 12B, 13A and 13B, the heat exchangers 3 aredesigned such that they angle inward and upward, creating a coolingtower effect, as seen on industrial boilers. This taper will serve tocreate thermal conduction that draws more cool air from near the bottomof the case 1 and allows it to migrate naturally upward and out of thetop of the heat exchangers 3. Cool-air inlet ports (not shown) at thebase of the heat exchangers can be covered with filter material in orderto keep dust and other foreign matter out of the heat exchangers, whileallowing air to enter. A fan or multiple fans may be used to aid in theupward flow of air through the cooling system.

As the cooled liquid is pumped back into the case 1, it may be sentthrough tubes or other deflection/routing means to injector headassemblies that serve to accelerate coolant across the most thermallyactive components. This accelerated liquid would help to createturbulent flow of coolant across the heated surface. This turbulent flowwould break down natural laminate flow, which is poor at conducting heatthrough a liquid because only the first few molecules of liquid that arein contact with the heated surface can actually take heat energy awayfrom the heated surface.

The computer 20 can also include external, removable storage drives suchas CD, DVD, floppy and flash drives (not illustrated). In addition,external IO, power button and other human interface controls (not shown)would attach to the pass-through connector 7 and be mounted on a rigidcircuit board or flex circuit.

FIG. 12B illustrates one possible flow path of liquid through themultiple heat exchangers 3:

-   -   1. Liquid is pumped out of the case 1 from the warm upper area        of the case 1 by the pump 13 through an inlet pipe 40 and out a        discharge pipe 42 (see FIG. 10); the discharge pipe 42 is        connected to an inlet 44 of the heat exchanger 3.    -   2. Liquid flows through and is cooled by the heat exchanger 3        that is also one side wall of the computer case.    -   3. A connection 46 allows liquid to pass through from the heat        exchanger 3 on one side of the case 1 to the heat exchanger 3 on        the other side of the computer case 1.    -   4. Coolant flows through the heat exchanger 3 on the other side        of the case 1.    -   5. Cooling liquid flows from the heat exchanger through a        passageway 48 back into the case 1 near the bottom thereof where        it is warmed by the heat-generating electronics and components        and rises back to the top of the case 1 and the cycle begins        again.

Alternatively, a single heat exchanger 3 as shown in FIGS. 13A and 13Bcan be used in the cooling system through the following steps.

-   -   1. Liquid is pumped out of the case 1 from the warm upper area        of the tank as in the embodiment in FIG. 12B.    -   2. Liquid flows through and is cooled by the heat exchanger 3        that is on one side wall of the computer case 1.    -   3. Cooling liquid flows back to the bottom area of the tank 1        through a passageway 50 where it is warmed and rises back to the        top of the case 1, and the cycle begins again.

The computer system can be cooled via active or passive convectioncooling, as shown in FIG. 14. Rather than forcing air from the front ofthe case to the back of the case, as seen in conventional designs, airis allowed to travel vertically. Heat rises, and the cooling system 22design takes advantage of this, as described in the following steps.

-   -   1. Cool air from underneath the computer is drawn upward as        shown by arrows 52.    -   2. The heat exchangers 3 are designed to allow the cool air to        flow upward between the heat exchangers and the outside of the        case 1. As heat is dissipated from the coolant inside the heat        exchangers 3, the cooler air around the heat exchangers 3 is        heated and rises.    -   3. The air flows through the heat exchangers 3 and is expelled        at the sides and top of the system. This rising air helps to        pull more cool air into the system, much like a cooling tower        for a boiler.

Air flow may be aided by the use of an air-moving device or devices suchas one or more fans mounted on the top or bottom of the cooling stack.However, for some applications only passive, convection-induced air flowmay be required.

FIGS. 15-16 illustrate a prototype computer 80 that incorporates theliquid submersion cooling system 22. Due to the clear case, the videoboards and pump are visible in the case and the heat exchangers arevisible, mounted on the sides of the case.

FIGS. 17-19 illustrate another embodiment of a personal computer 100employing an alternative liquid submersion cooling system 102. Thecomputer 100 includes a case 104 that has a liquid-tight interior space106 (FIG. 20) designed to be leak-proof so that it can be filled with acoolant liquid. As used herein, the word “case” is meant to include ahousing, an enclosure, and the like. In the illustrated embodiment, theside wall 107 of the case defines at least one side of the interiorspace 106, and a portion 109 of the side wall 107 is made oftranslucent, preferably transparent, material to allow viewing insidethe space 106. The material used for the portion 109 can be any materialsuitable for forming a leak-proof container and, if viewing of theinternal computer components is desired, the material should betranslucent or transparent. An example of a suitable material is apolycarbonate.

The case 104 also includes non-liquid tight space 111 next to theliquid-tight interior space 106 in which components of the computer 100and the cooling system 102 are disposed as described below.

With reference to FIGS. 17 and 20, the case 104 includes a lid 108 thatcloses the top of the case 104, but which can be removed to permitaccess to the spaces 106, 111. The lid 108 includes a seal 113 (shown inFIGS. 21 and 22) for forming a liquid-tight seal with the interior space106 of the case when the lid 108 is in position closing the case. Inaddition, the lid 108 includes a handle 110 that facilitates grasping ofthe lid 108 and lifting of any internal computer components connectedthereto out of the interior space 106. The lid 108 also includes apass-through connector 112 (partially visible in FIG. 22), similar infunction to the pass-through connector 7, to which a motherboard 114assembly is connected, and which permits pass-through connections suchas USB ports, video card connections, etc., through the lid 108 to theinside of the space 106 and to the outside of the space 106.

For safety, an AC current cut-off mechanism 115 is also provided, asshown in FIGS. 31A-C, such that when the lid 108 is opened, electricalpower in the computer is shut off, preventing operation of anyelectrical components. For example, the mechanism 115 may beaccomplished by routing AC power through a bridge board 400 that iscontained in, or otherwise connected to, the lid 108. The board 400 isconnected to the motherboard assembly 114 comprised of a motherboard 302and a support 300 member.

The board 400 includes an AC power socket 402 for receiving AC power. Aneutral line 404 and a ground line 406 leads from the power socket 402to a pass-through connector 112 leading to the interior space 106. Inaddition, a hot or live wire 408 leads from the socket 402 to a secondpass-through connector 112 leading to the space 111, passes under theboard 400 and back to the top of the board 400 to a return portion 410that connects to the pass through connector 112 to pass AC power intothe interior space 106.

An external board 412, illustrated in FIG. 31C, is fixed in the space111. The board 402 includes a u-shaped connector 414 at the top thereof,one end of which connects to the hot wire 408 and the other end of whichconnects to the return portion 410 when the lid 108 is in place.

When the case is opened by removing the lid 108, the hot wire 408becomes disengaged from the connector 414 on the external board 412,opening the electrical circuit and disconnecting AC power from theinterior space. The current cut-off mechanism 115 may also beaccomplished by routing AC power through two pins on the bridge board400. These pins would be shorted, passing current back to the externalboard 412. When the case is opened, the bridge board 400 becomesdisengaged from the connector 414 on the external board 412.

The lid 108 also includes an opening 116 through which liquid can beadded into the space 106. The opening 116 is closed by a removable capwhich is removed when liquid is to be added. The lid 108 can alsoinclude a lock mechanism (not shown) that locks the lid in place.

With reference to FIG. 20, the case 104 can include a drain valve 118(shown schematically) that can be opened in order to drain liquid fromthe case. The valve 118 can be any type of valve that can be opened andclosed, preferably manually, for draining the case. The valve 118 isillustrated as being positioned at the bottom of the interior space atthe bottom of the case 104. However, the valve can be positioned at anyother suitable location on the case. The front portion of the case 104can have a touch screen display that allows users to run the computer100 from the front without plugging in a monitor.

The motherboard assembly 114 acts as a support for many of the internalcomponents of the computer 100. The motherboard assembly 114 isremovable and disposed in the interior space 106 to permit themotherboard assembly to be lifted from the case when the lid 108 islifted upward. With reference to FIGS. 20-22, the motherboard assembly114 includes a support member 300 on which is disposed a motherboard 302that supports the submerged components.

The motherboard assembly 114 is fixed to the lid 108 via flanges 122 atthe top end of the motherboard 114, shown in FIG. 24, that connect tothe pass-through connector 112. In addition, a pair of tabs 123 that arefixed to the support member 300 are connected to the lid 108.

An exemplary layout of the motherboard components is illustrated in FIG.23. The layout is designed to render the motherboard nearly orcompletely 302 wire-free and facilitate movement of cooling liquid inthe interior space 106. The motherboard 302 is illustrated as havingmounted thereto four CPUs and/or GPUs 124, video/motherboard memorycards 126, memory cards 127, power supply 128, and controller chips 130.These components are laid out relative to each other to define a numberof vertical and horizontal liquid flow channels that aid in the flow ofliquid. For example, vertical channels include channel 132A between theCPUs/GPUs 124, channels 132B between the controller chips 130, andchannels 132C between the CPUs/GPUs and the memory cards 126, 127.Horizontal channels include, for example, channel 134A between theCPUs/GPUs, channel 134B between the CPUs/GPUs and the controller chips130, and channel 134C between the CPUs/GPUs and the power supply 128. Aplurality of sets of light-emitting diodes (LEDs) 136, that can producea desired color/wavelength of light, such as ultraviolet, can also bemounted to the motherboard 114 at dispersed locations. When illuminated,the LEDs 136 give the liquid in the interior space 106 a luminescentglow.

To help dissipate heat, heat sinks can be affixed to some or all of theheat-generating components on the motherboard 302. The use of heat sinkswill depend on the amount of heat generated by a particular componentand whether it is determined that additional heat dissipation than thatprovided by direct contact with the liquid is necessary for a particularcomponent.

As shown in FIGS. 20-23, heat sinks 140 are shown attached to theCPUs/GPUs 124 and the controller chips 130. The heat sinks 140 eachcomprise a plurality of elongated fins 142 that extend from a base plate144 fixed to the component. The fins 142 and plate 144 conduct heat awayfrom the component. In addition, the fins 142 define flow channelstherebetween that allow the cooling liquid to flow through and past theplurality of fins to transfer heat to the liquid.

Heat sinks 150 are also attached to the memory cards 126, 127 and thepower supply 128. The heat sinks 150 are similar to the heat sinks 140,including fins 152 connected to a base plate 154 fixed to the component.However, the fins 152 are short, having an axial length significantlyless than the fins 142. Nonetheless, the fins 152 define flow channelstherebetween which allow the cooling liquid to flow through and past theplurality of fins to transfer heat to the liquid.

As described above, the motherboard assembly 114 is removable anddisposed in the interior space 106 to permit the motherboard assembly tobe lifted from the space when the lid 108 is lifted upward. Withreference to FIG. 24, the interior space 106 of the case 104 includes apair of channels 160 at opposite ends of the walls that define theinterior space. Each channel 160 extends from the top of the walls tothe bottom, and are continuous from top to bottom. As shown in FIGS. 22and 24, the side edges of the motherboard assembly are provided withslides 162 that are sized and configured to slide within the channels160. The channels 160 and the slides 162 help guide the motherboardassembly 114 when it is lifted upward from the case and when it islowered back into the interior space.

With reference to FIGS. 21-24, one or more slide locking mechanisms 170can be provided to retain the motherboard assembly 114 at a raisedposition outside the interior space 106. Two slide locking mechanisms170 are illustrated. However, a single slide locking mechanism could beused if found sufficient to retain the motherboard assembly at theraised position. By keeping the motherboard assembly raised, maintenanceand/or replacement of motherboard components is facilitated, while alsoallowing liquid to drain down into the interior space 106 when theassembly 114 is lifted upward.

The slide locking mechanisms 170 can have a number of configurations.The illustrated embodiment is shown to include a stop member 172 thatforms part of the slide 162. The stop member 172 is pivotally connectedto the motherboard assembly so that it can rotate between the positionshown in FIGS. 21-23 and the position shown in FIG. 24. The stop member172 is biased by a spring (not shown) to bias the stop member in acounterclockwise direction (when viewing FIG. 21) so that when themotherboard assembly is lifted upward, the stop member(s) automaticallyrotate to the position shown in FIG. 24 when the stop members 172 clearthe channels 160.

At the position shown in FIG. 24, the stop member 172 is prevented fromfurther rotation in the counterclockwise direction to prevent themotherboard assembly from falling back down into the interior space 106due to interference between the stop member(s) 172 and the structureforming the channels 160. To release the slide locking mechanisms 170,the motherboard assembly is lifted further upward, and the stopmember(s) manually rotated in a clockwise direction to the positionshown in FIGS. 21-23. The assembly is then lowered down into the case.

With reference to FIGS. 17 and 20, the submersion cooling system 102includes a heat exchanger 180 mounted in the space 111 within the case104, a pump 210 mounted on the motherboard 302 inside the interior space106, and a dielectric cooling liquid within the interior space 106. Theinterior space should contain enough dielectric cooling liquid tosubmerge the components that one wishes to be submerged. For example,the cooling liquid may substantially fill the interior space 106,whereby all heat-generating components on the motherboard are submerged.The cooling system 102 is designed to direct heated dielectric liquidfrom inside the space 106 and into the heat exchanger 180 outside thespace 106 where the liquid is cooled. The cooled liquid is then returnedto the space 106.

The heat exchanger 180 is positioned outside of the space andsubstantially forms an outer wall of the computer 100 as shown in FIG.18. The heat exchanger 180 is configured to allow passage therethroughof the liquid for cooling. In the illustrated embodiment, the heatexchanger 180 is of a size to form substantially one wall of the case104. With reference to FIG. 26, the heat exchanger 180 includes an inlet182 through which cooling liquid enters, an outlet 184 through whichcooling liquid exits, and at least one flow path for cooling liquidthrough the heat exchanger extending from the inlet 182 to the outlet184.

The heat exchanger 180 can take on a number of different configurations,as long as it is able to cool the liquid down to an acceptabletemperature prior to being fed back into the space 106. An exemplaryconfiguration of the heat exchanger 180 is shown in FIGS. 26 and 27. Inthis embodiment, the heat exchanger 180 comprises a plurality ofidentical plates 186 that are connected together. Each plate 186includes a hole 188, 190 at each end that during use form plenums thatreceive the dielectric liquid. The plate 186 also includes a firstplurality of holes 192 defined by bosses that extend in one direction,and a second plurality of holes 194 defined by bosses that extend in theopposite direction. The holes 188, 190 are also defined by bosses thatextend in the same direction as the bosses defining the holes 192. Inaddition, a central portion 196 of the plate 186 is bulged in thedirection of the bosses of the holes 188, 190, 192, so that the oppositeside of the plate 186 is recessed 198 below a surrounding rim 200.

To form the heat exchanger 180, a first plate 186A is flipped over asshown in FIG. 27, and the two plates 186A, 186B then secured togethersuch as by soldering along the rim 200. The two holes 188 are aligned atthe top, and the two holes 190 are aligned at the bottom. In addition,the bosses that define the holes 194 engage with each other to form anumber of air passages between the two plates 186A, 186B. The recesses198 allow liquid to flow downward from the holes 188, past the engagedbosses of the holes 194, and down to the holes 190.

A third plate 186 is then connected to one of the plates 186A, 186B,with the third plate being flipped over relative to the plate to whichit is connected. The bosses that define the holes 188, 190 will engageeach other, as will the bosses that define the holes 192. This willcreate a series of air flow paths 202 on the outside of the heatexchanger as shown in FIG. 26. This process of adding plates 186 isrepeated to create the size of heat exchanger needed. For the two platesat opposite ends of the heat exchanger 180, the holes 192, 194 will beclosed off to prevent escape of liquid. In addition, an inlet fitting204 defining the inlet 182 will be connected to the boss defining theopening 188, while an outlet fitting 206 defining the outlet 184 will beconnected to the boss defining the opening 190. At the opposite end ofthe heat exchanger, the openings 188, 190 are closed by suitable caps208.

In use of the heat exchanger 180, liquid to be cooled flows into theinlet 182 and into the plenum at the top of the heat exchanger definedby the holes 188. The liquid is able to flow downward in the recesses198 past the bosses of the holes 194. As it does, the liquid transfersheat to the bosses. At the same time, air can flow into the alignedbosses of the holes 194 to pick up heat. Air also flows into the flowpaths 202 for additional heat exchange with the bulged central portion196. The cooled liquid collects in the plenum defined by the alignedholes 190, and is pumped through the outlet 184 and back into the space106 by the pump 210.

Referring to FIGS. 20, 22 and 23, the pump 210 is mounted on themotherboard 302 and in use is submerged in the dielectric liquid. Thepump 210 is sized to be able to circulate liquid to outside the space,through the heat exchanger, and back into the space. The pump 210 isillustrated as a centrifugal pump having an inlet 212 and an outlet 214.The inlet 212 receives liquid therethrough from the space 106, and pumpsit through the outlet 214 connected to an outlet port 218 formed on thelid 108. The outlet port 218 extends through the lid 108 and is fluidlyconnected to the heat exchanger inlet 182 by suitable tubing. The heatexchanger outlet 184 is fluidly connected by suitable tubing to an inletport 222 formed through the lid to direct liquid back into the space106.

In areas where there is significant heat, direct impingement cooling canbe used to provide localized cooling. In particular, as shown in FIGS.20, 22, and 23, a spray bar assembly 230 is connected to the inlet port222. The spray bar assembly 230 includes a central passageway 231extending along the vertical channel 132A, and plurality of branches orvents 232 that extend along the horizontal channels 134A-C (and at thebottom of the space 106). The branches 232 include holes 234 (FIG. 20)to direct cooled liquid directly onto the components 124, 126, 127, 128,130. The holes 234 are in the top of the branches 232 to direct liquidupwardly. However, holes could also be provided at the bottom of thebranches to directed liquid downwardly onto the components.

An air-moving device can be provided to create a flow of air past theheat exchanger. A number of different air-moving devices can be used,for example, a fan or an ionization device. The drawings illustrate theuse of a fan 240 to create air movement past the heat exchanger 180. Thefan 240 is best seen in FIGS. 20, 25, and 28. The fan 240 is positionedat the bottom of the computer 100 at the base of the heat exchanger 180.In the illustrated embodiment, the fan is a squirrel-cage type fan withan air outlet 241 that extends substantially across the entire length ofthe heat exchanger in order to create air flow across the entire heatexchanger. An air filter 242 is located in front of the inlet of the fan240 in order to filter the air. The air filter 242 can be any suitabletype of air filter, for example, a high-efficiency particulate air(HEPA) filter. The filter 242 is mounted so as it is able to slide andbe removable from the case 104 by pulling on a handle 243. This permitsthe filter 242 to be cleaned or replaceable with a replacement filter.Air is drawn into the filter and the fan via a series of air vents 244(FIG. 18) on the side of the computer.

The computer 100 can also include additional features, such as a drivemechanism 250 external to the case 104. The drive mechanism 250 can be aDVD drive, a floppy drive, a CD drive, a Blu-ray drive, HD drive, andthe like. In addition, one or more hard drives 252 are accessible fromthe opposite side of the case 104. The hard drives 252 can be mounted soas to permit easy replacement with replacement hard drives.

In some embodiments, the hard drive 252 may be disposed within theinterior space 106 of the case, submerged in the dielectric liquid. Inthese embodiments, it is necessary to equalize air pressure within thehard drive and the exterior of the space 106. FIGS. 29 and 30A-Cillustrate a snorkel attachment 260 that can be connected to a breatherhole 261 (see FIG. 30A) on a hard drive to aid in achieving the pressureequilibrium. The snorkel attachment 260 includes a circular cap 262 thatis designed to fit around the breather hole 261 (see FIG. 30B) and forma liquid tight seal with the hard drive 252 to prevent entry of liquid.A fitting 264 extends from the cap 262, and a breather conduit 266connects to the fitting 264. The breather conduit 266 can be directed tothe outside of the space 106, or the conduit 266 can connect to afitting extending through the lid 108. The snorkel attachment 260permits achievement of pressure equilibrium between the hard drive andoutside air pressure, allowing the hard drive to function properly whilesubmerged in the dielectric liquid.

The dielectric liquid that is used in the computer 100 can be any of thedielectric liquids discussed above. In addition, a soy-based dielectricliquid can be used. If desired, a colorant material can be added to thedielectric liquid to make the liquid a particular color. Because theportion 109 of the side wall 107 is clear, adding a colorant to theliquid will change the visual impact of the computer.

1. A liquid submersion cooled computer, comprising: a case having aliquid-tight interior space; a lid removably connected to the case forclosing a top of the interior space, the lid including at least onepass-through connector; a motherboard disposed in the interior space andattached to the lid, the motherboard having a top end with electricalcontacts engaged with the pass-through connector that permitsinputs/outputs and/or power to be passed to the motherboard; a pluralityof components mounted on the motherboard, including one or more of aplurality of processors, a plurality of memory cards, a plurality ofgraphics cards, and a plurality of power supplies; a dielectric coolingliquid within the interior space and submerging at least one of thecomponents on the motherboard so as to be in direct contact therewith;and an impingement cooling system that includes a plurality of tubes fordirecting a flow of the dielectric cooling liquid directly onto two ormore of the plurality of components.
 2. The liquid submersion cooledcomputer of claim 1, further comprising a liquid pump disposed in theinterior space.
 3. The liquid submersion cooled computer of claim 2,wherein the liquid pump is mounted on the motherboard.
 4. The liquidsubmersion cooled computer of claim 1, comprising a plurality ofprocessors, a plurality of memory cards, a plurality of graphics cards,and a plurality of power supplies mounted on the motherboard.
 5. Theliquid submersion cooled computer of claim 1, further comprising a heatsink connected to at least one of the components mounted on themotherboard, the heat sink including a plurality of fins that extendfrom a base plate, the fins defining liquid flow channels therebetween.6. The liquid submersion cooled computer of claim 5, wherein the finsextend in a direction generally perpendicular to the motherboard.
 7. Theliquid submersion cooled computer of claim 1, further comprisinglight-emitting diodes mounted on the motherboard.